1. Field of the Invention
This invention relates to electronic timepieces and more particularly to circuits for achieving the voltages required to operate electronic timepiece components which require higher than battery voltage.
2. Prior Art
The voltage translator of this invention is useful for converting a low battery voltage to the relatively high voltage necessary for operating a liquid crystal display in a crystal oscillator controlled watch. A serious problem exists in the design of electrically energized watches in that very little space is available for the power source, and consequently the power available to operate the watch is seriously limited. Typically one or at the most two 1.5 volt cells are used to drive the watch and the current drain must be held to an absolute minimum in order to achieve a battery life of at least one year, the life deemed necessary in order to have a salable product.
Various schemes have been developed to operate relatively standard mechanical watches from such a limited energy source and reasonably satisfactory timepieces have been made. Recently, a demand for watches more accurate than previously available has appeared, probably as a result of the modest increase in accuracy attained by some of the electrically energized watches over the traditional mainspring driven watches.
Quartz crystal oscillators are known to be highly accurate, and this characteristic has led to consideration of crystal oscillator control of mechanical movements to achieve the desired accuracy, and, as a consequence, to the possibility of direct digital readouts using light emitting diodes or liquid crystal displays rather than standard watch faces with hands.
Liquid crystal displays are an attractive choice for a readout since they require very little operating power and are susceptible to control by solid state logic. Unfortunately, the lower level of voltage required to operate existing displays is about 10 volts, with 15 volts being a desirable operating voltage.
There are numerous methods of increasing direct current voltages known to the prior art, but for the most part the complexity and inefficiency factors prohibit their use in the small space and limited energy environment of a battery operated watch.
The invented circuit converts the low voltage available (commonly 3 volts) to the 15 volts required to operate the display using a minimum volume of components and resulting in a maximum of efficiency.